Whats the easiest way to animate a toy house being built from the ground up?
My suggestion would be to use python to animate the individual blocks.

I would pick a landing time based on the z coordinate of the block and a little bit of randomness (but not so much randomness that a block with a different Z coordinate could land before one below it).

http://web.purplefrog.com/~thoth/blender/python-cookbook/sweep-animate-size.html includes some examples of setting keyframes like

    fr = obj_to_frame_f(obj)

    obj.scale =(0,0,0)
    obj.keyframe_insert(data_path='scale', frame=fr-timescale-timescale2)
    obj.keyframe_insert(data_path='scale', frame=fr+timescale+timescale2)
    s = 0.9
    obj.scale=(s,s,s)
    obj.keyframe_insert(data_path='scale', frame=fr-timescale)
    obj.keyframe_insert(data_path='scale', frame=fr+timescale)


Although you'll be animating data_path='location' instead of scale.